Moderate stress, anxiety not a factor in fertility, pregnancy

The weight of evidence suggests that moderate levels of stress and anxiety do none of the things we fear. (Photodisc)

Anxiety is not only the most common mental problem in the United States, it verges on a national obsession. Last year, New York Magazine declared it the signature diagnosis of our time with Xanax as its pharmacological mascot, taking over from depression and Prozac in the 1990s. The New York Times devotes an entire ongoing series to probing the anxious mind. And the online forum the Edge asks as its key question for 2013: "what should we be worried about?" All this worrying represents our own apocalyptic myopia. Before we know it, we're not just worrying about love, death, sickness, children, money — we're worrying about the worrying itself.

The punishing epicenter of anxiety obsession is women's fertility and pregnancy. Women who have trouble conceiving often believe that their own distress is making it harder to conceive. And who can blame them, when even fertility centers urge them to create a "stress-free environment." And of course, with pregnancy, the worry doesn't end — it's just beginning. Scattershot reports link anxiety to miscarriage or preterm birth with random speculation, as in: Will Kim Kardashian's divorce stress hasten the birth of her baby? Will emotional symptoms during pregnancy cause developmental delays? A finding here, an anecdote there — women can easily get the wrong idea.

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And the reigning impression is wrong: The weight of evidence suggests that moderate levels of stress and anxiety do none of the things we fear. They seem not to affect whether women are able to conceive, whether they carry the fetus to term, or whether their kids reach normal developmental milestones. (If anything, some maternal stress during pregnancy seems to make kids mature a little faster.) This doesn't mean, of course, that women with anxiety shouldn't seek care and support. But they should do so for their own sakes — not because distress will ruin their shot at motherhood or somehow damage their fetuses.

Take fertility. In 2011, British psychologists pulled together data from 14 studies of in vitro fertilization. In each study, researchers asked women to assess their emotional distress, anxiety or depression. Then they followed them through a single cycle of fertility treatment to see whether they got pregnant or not. The smaller individual studies arrived at disparate results, but the meta-analysis rolling up all the findings, which included over 3,500 women and appeared in the BMJ, was fairly definitive: Women's emotional state before IVF bore no relationship to whether the treatment worked. In other words, women with more extreme levels of anxiety or depression were just as likely to get pregnant after a single cycle as women with milder levels. "It was a great relief," said psychologist Jacky Boivin, who has counseled women struggling with infertility for years and who led the meta-analysis team. (Less clear is whether extreme levels of stress, as in war or famine, suppress natural fertility. They may, but the effect may also turn out to be temporary, according to Boivin: "At some point, even in harsh environments, reproduction tends to come back.")

What about during pregnancy? The old idea that stress causes miscarriage isn't supported by the data and seems, thankfully, to have lost some of its traction. The current angst, though — that emotional symptoms can lead to preterm birth — threatens to torment women at least as much. It's true that you can find smaller studies that fuel the fear. But consider this large, population-based work, in which researchers interviewed over 78,000 Danish women. Those who reported higher levels of life stress and more emotional symptoms like anxiety when they were 30 weeks pregnant did tend to give birth earlier. But the difference was pretty minimal: The women with the highest life-stress scores gave birth, on average, about two days before women with lower scores. Those who reported the most intense emotional symptoms had pregnancies that were just two-and-a-half days shorter. This isn't an effect that matters in children's lives.

Finally, there's the question of how Mom's distress during pregnancy affects kids' actual development. Here, too, the data are mixed. The strongest studies try to separate the influence of maternal stress during pregnancy from the stress or adversity, after birth, in children's home environments. (Often there is a correlation between the two.) This research also tries to assess children directly, rather than relying on parents' reports about their behavior. The most persuasive of these papers suggest that mild to moderate stress during pregnancy doesn't hamper babies' maturation — if anything, it may slightly hasten it. In one study, fetuses whose mothers reported higher levels of distress tended to be more active in utero, a positive developmental sign. In another study, newborns of more distressed women conveyed electrical signals more rapidly along the nerve from the ear to the brain, also a marker of neural development. And in a study of toddlers, the results were more striking still: Two-year-olds who were exposed in utero to more maternal distress, including depression or anxiety, scored higher on a standard measure of child development. "It just looks like they mature a little faster," said Janet DiPietro of Johns Hopkins, who conducted these studies. In other words, there is little evidence that maternal stress during pregnancy is bad for babies.

DiPietro, who is one of the foremost experts in the world on fetal outcomes, says she finds the continued intensity of work on these questions puzzling, given the findings so far. "I'm trying to get out of the stress stuff!" she told me. So should the rest of us. It's time to stop worrying that our worrying will prevent us from reproducing successfully. Survival of the species, it turns out, just isn't that fragile.